NXRRSET

Chris Buxton cbuxton at menandmice.com
Wed May 6 17:17:31 UTC 2009


On May 6, 2009, at 7:49 AM, Thilanka Samarasekera wrote:
> Hello,
>
> I am running BIND version 9.2.3 on a Solaris 9 box. Every now and  
> then I will see the following in my DNS cache:
>
> domain.com.       458     \-AAAA  ;-$NXRRSET
>
> If I force a MX record lookup it does get the correct MX records for  
> "domain.com". The explanation I have for "NXRRSET" is "Its the  
> number od queries the name server handled that resulted in responses  
> saying that the type of record the querier requested didn't exist  
> for the domain name it specified". If do a MX record look for  
> "domain.com" it does get the correct entries and caches it for the  
> specified TTL. My question is how do I go about identifying what's  
> causing my BIND server to cache a query with the flag "NXRRSET" ?


The query getting the negative response here is for an AAAA record  
named domain.com. For example, there might be:

example.com.  MX  10  mx.example.com.
mx.example.com.  A  192.0.2.1

Your cache might then end up with an NXRRSET (no such resource record  
set) for mx.example.com/IN/AAAA, because the mail server is looking  
for IPv6 addresses for the mail server.

Chris Buxton
Professional Services
Men & Mice




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